The principal objective of proposed research is to elucidate the relationship between the process of the sexual differentiation of the brain and the hypothalamic regulation of food intake and body weight. We plan to identify those components of the regulation of food intake and body weight which are sexually dimorphic. To date sexual dimorphism appears to be restricted to chronic or long-term regulation. After we have indentified a number of sexually dimorphic parameters, we will determine whether these are altered by the perinatal hormone environment and/or modulated in the adult by gonadal hormones. In intact or gonadectomized male, female, androgenized female and neonatally castrated males, food intake and body weight will be evaluated following chronic insulin treatment, forced exercise, after diet dilution, or alterations in diet palatability, or different periods of food deprivation. Gold thioglucose will be implanted directly into the ventromedial hypothalamus to destroy glucose responsive cells postulated to regulate food intake in the long-term situation. In these animals the effects of estrogen administration on food intake regulation will be monitored in an attempt to elucidate the side of action of this steroid in the central regulation of energy balance. It is hoped that these studies will lead to greater understanding of the interactions between gonadal activity and the regulation of food intake and body weight, particularly those interactions unique to the developing animal. BIBLIOGRAPHIC REFERENCES: Nance, D. M. and Gorski, R. A. (1975). Neurohormonal determinants of sex differences in the hypothalamic regulaion of feeding and body weight. Pharm. Bicohem. and Behav. 3, Suppl. l: l55-l62. Nance, D.M., Gorski, R.A. and Panksepp, J. (l976). Neural and hormonal determinants of sex differences in food intake and body weight In: Hunger: Basic Mechanisms and Clinical Implications, Novin, D., Wyrwicka, W. and Bray, G.A. (eds.), Raven Press, New York, pp.257-27l.